Fire near Gela (IT)

What the satellites measured

This fire was tracked from 7 September at 13:08 to 12 September at 03:34, that is 5 days, through 17 satellite detections. The detected extent reaches 481 ha.

Detected extent

481 ha

Cumulative power

1,147 MW

Peak power, one pixel

339 MW

VIIRS and MODIS detections

17

These four figures cover the polar orbits alone, the ones that measure an area. The pass table below also counts geostationary detections, more frequent but too coarse for geometry, and its power column sums a whole pass where the peak above is that of a single pixel.

“Detected extent” is not “burned area”: it is the union of the ground footprints of the satellite pixels, and a 375 m pixel counts in full even when only a forest edge is burning. Compared with press figures it is in practice one and a half to three times the area reported. Detections taken at the edge of the scan swath, too coarse to measure anything at all, are excluded. These figures come from thermal detection and are not an official assessment: only the emergency services and the competent authorities are authoritative.

Replay how the fire spread

The map is framed on this fire and loads only its detections. The timeline below covers the whole known life of the fire, from the first trace, satellite or report, to the last announcement from emergency services, and the ticks on the bar mark those announcements. Detections often stop before containment: a fire stops radiating once it stops spreading, which is exactly when it is declared contained. “1 h” shows what is burning within an hour of the chosen moment : the map then follows the power curve below and empties when it falls. “12 h” stacks twelve hours , as the home map does, where stacking avoids an empty screen between two satellite passes. Both are true, but they say different things.

How the radiative power evolved

One point per satellite pass: the sum of the fire radiative power measured over the fire. This is the curve that says whether the fire eased off or picked up again, which no cumulative figure shows. The window covers 7 days; beyond that, clustering would merge two successive fires in the same place.

Satellite passes in detail

2 other fires near Gela (IT)

Separate fires, apart in time or in space, not pieces of this one. A single municipality can have several over one summer, and a forest massif often covers more than a hundred square kilometres.

• 31 July to 14 August1,247 ha
• 18 to 21 July1,199 ha

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